Review by Klaus Schroiff, published December 2016

Introduction

Canon L class lenses are aligned to professional use and this also applies to the EF 24-105mm f/4 USM L IS II. That being said, it doesn't seem to be fully made of metal as you might expect at least. The inner lens tube seems to be made of plastic and we've got the impression that this is also applies for parts of the outer body. Still the quality perception is on a very high level and the weather sealing provides some additional peace of mind as well. Like most of its fellow standard zoom lenses, it extends when zooming towards the tele end. However, the inner lens tube shows no wobbling even when fully extended. We didn't observe any zoom creeping but Canon implemented a transport lock nonetheless. Both the zoom and focus rings operate smoothly. An improved lens hood (with click lock) is also part of the package. On the optical side, Canon didn't reinvent the wheel when looking at the lens' optical design and even Canon's own MTF curves don't look overly exciting (...). However, unlike the predecessor, the mk II features Canon's new ASC (Air Sphere Coating) which is supposed to suppress flare.

Obviously Canon didn't want to experiment thus the AF system continues to rely on the speedy ring-type USM drive with full-time manual (FTM) focusing. Unfortunately we weren't really impressed by its accuracy. We had to test two samples (more this later) and both were often WAY off (back-focusing) especially at 24mm where the camera focused substantially beyond infinity at long distance shots. While a lens should be able to do that (in order to compensate of potential thermal effects), it spoiled many of our real world sample images.
The old mk I version of the lens featured an image stabilizer already but it was only good enough for a equivalent gain of 2.5 f-stops. The updated lens is rated at 4 f-stops although we'd still recommend to avoid the extremes of that statement.

Below is a paper-spec comparison to the old Canon EF 24-105mm f/4 USM L IS.